Softening of acid-treated fabrics



Patented July 14, 1925..

UNITED STATES PATENT OFFICE.

ROBINSON PERCY FOULDS AND FRANK LESLIE BARRETT, OF MANCHESTER, ENGLAND.

SOFTENING OF I ACID-TREATED FABRICS.

No Drawing.

To all whom it may concern.

Be it known that we, ROBINSON PERCY FoULDs and FRANK LESLIE BARRETT, both British subjects, both residing in Manchester, in the county of Lancaster and Kingdom of England, have invented certain'new and useful Improvements in Softening of Acid-Treated Fabrics, of which the following is a specification.

This invention relates to the treatment of cellulosic fabrics especially cotton fabrics which have been treated with sulphuric acid of parchmentizing strength.

The invention will be described with special reference to the treatment of fabrics which have also been compressed but the invention is not limited to such compressed fabrics.

It is known when cotton and other fabrics are compressed (e. g., by embossing or calendering hot) and then parchmentized, the cloths so treated are usually of a stiff character and resemble linen in some respects but they are unsuitable for many purposes for which cotton goods are required.

The object of the present invention'is to obtain asofter handle and feel on goods which have been submitted to the above or similar processes, while retaining some of the advantages obtained by an acid treatment.

The advantages of having a fabric which has been acid treated and which is also soft, are many. The finishes to be obtained on such'fabrics are valuable owing to their permanency.

Broadly the present invention consists in subjecting the parchmentized fabric to the action ofa weaker sulphuric acid for the purpose of softening it; other relatively dilute parchmentizing agents may be used and are included in the general term softening acid, i. e., an acid and certain salt so-' lutions which are not strong enough to exert 'a definite parchmentizing action but still capable of affecting the fibres in the manner hereafter described. 'VVe exclude caustic alkalis' from the scope of the terms soften- 1 ingacid andparchmentizing reagent.

If'the fabric is fully parchmentized, we findthat it is not usually possible'to soften it by this treatment, unless it is subsequently" compressed prior to softening.- In general Application filed November 25, 1924. Serial No. 752,266.

therefore, the parchmentizatio-n should be limited or incomplete either by virtue of short exposure, dilution of acid, etc., ,or by compressing prior to parchmentizing in which case the compressed parts are less attacked and thus only parchmentized to a limited extent. If, on the contrary, parchmentization is followed by compression, results can still be obtained even when the action of the acid is more complete.

We find that the greater the extent of parchmentization the longer must be the exposure to the softening acid which may also be increased in strength up to the limit subsequently mentioned.

The best results are obtained by compressing, parchmentizing and softening in the order specified but some result can be obtained in the alternative processes described either with or without compression.

We will accordingly describe the invention in detail with inclusion of the compression step but the invention is not so limited.

We have found that material which has been compressed and acid treated to give a permanent pattern, or all over effect can be rendered soft and free from harshness (where the fabric has been compressed) by a subsequent treatment with weak sulphuric acid, preferably from 1.40 to 1.55 spec. grav. It is essential to avoid a parchmentizing effect and yet the acid should be strong enough to exert some (softening) effect on the cotton.

k The process may be a continuous one in which the compressed material is run from a strong acid into a weaker one, or the first acid treatment may be given and the softening process proceeded with? subsequently with intermediate washing. The fabric may A slight. rise in the strengths specified this will not be injurious.

Intermediate steps may be introduced in the process before the softening acid process is used. For instance after the embossing and acid treatment the usual finishing methods for breaking down stiff fabrics may be used and the softening process used as a last step.

The effects to be obtained vary greatly according to the cloth to be used, the conditions of embossing and the length of time given in the parchmentizing acid.

The softened material may be dyed or subsequently finished by any of the ordinary finishing processes.

The limits within which we have found the process to be most efficient when carried on in two stages are from 1.50 to 1.55 spec. grav. for the second acid bath. Partial softening can however be obtained down to 1.40 spec. grav. but this takes a longer period of time.

Other parchmentizing agents which have in general the properties of sulphuric acid of the strengths used can also be utilized for softening, e. g., phosphoric, nitric or hydrochloric acids, or zinc chloride if used at suitable strengths (less than ordinary parchmentizing strengths). Diluents may be added provided that they do not make the liquid entirely inert.

The process can be applied "to fabric parchmentized with acid alone or with acid formaldehyde mixture (see British Patent.

The process can also be applied to treat fabrics which have been compressed and then treated with acid below, parchmentizing strength (see British Patent No. 200,881 on properties of acid below 1.55 spec. grav. with addition of formaldehyde) in which case both acid baths will be below 1.55. Or we may first parchmentize with acid above 1.55 then compress and finally soften or we may treat with acid below 1.55 compress and finally soften with a bath of weak acid as described.

Example.

A heavy plain cloth is embossed either with or without pattern and treated with sulphuric acid of 1.665 spec. grav. (without or preferably with the addition of formaldehyde solution of 40%) for 5 secs. and run straight into weak sulphuric acid of 1.45 spec. grav. for 1 min. The softening action takes place, according to the desired softness required, after which the fabric is washed and finished off in the ordinary way.

By the expression cellulosic fabrics we meantextile fabrics capable of being parchmentized and we do not include such materials as acetyl cellulose or paper, unless otherwise stated, it willbe undersgood that additional treatment steps may be interpolated between the various steps specified in the claims, or performed before or after any of said steps.

We declare that what we claim is:

1. The step in the process of treating cel lulosic fabrics which comprises softening an incompletely parchmentized fabric by exposure to a parchmentizing reagent below parchmentizing strength.

2. The step in the process of treating 'cotton fabrics which comprises softening an incompletely parchmentized fabric by exposure to an acid below parchmentizing strength.

3. The step in the process of treating cellulosic fabrics which comprises softening an incompletely parchmentized fabric by exposure to sulphuric acid of less than 1.55 spec.

grav.

4. The step in the process of treating cellulosic fabrics which comprises softening an incompletely parchmentized fabric by exposure to dilute sulphuric acid of about 1.50 spec. grav.

5. The step in the process of treating cellulosic fabrics which comprises softenlng a parchmentized fabric having an embossed pattern by exposure to a parchmentizing reagent of less than parchmentizing strength. j

6. The process of treating cellulosic fabric which includes parchmentizing the fabric to a limited extent and exposing said fabric to the action of an acid softening liqpid. The process of treating cellulosic fabric which includes parchmentizing the fab- 1 ric with sulphuric acid to a limited extent and then exposing said fabric to the. actionv of an acid softening liquid. j

8. The continuous process of treating cellulosic fabric which includes parchmentizing the fabric to a limited extent and then running the undried fabricinto an acid softening liquid. 4

9., The process of treating cellulosic fabric which includes parchmentizing the fabric to a limited extent and then exposing said'fabric to the action of an acid softening liquid without the interpolation of an intermediate treatment.

10. The process of treating cellulosic fabric which comprises compressing the fabric, parchmentizing it and then exposing it to the action of an acid softening liquid.

11. The process of treating cotton fabric which comprises compressing the fabric, parchmentizing it and then exposing it to the action of an acid softening liquid. 1

12. The process of treating cellulosic fabric which comprises compressing the fabric, parchmentizing it with sulphuric acid and then exposing it to the action of an acid softening liquid.

13. The process of treating cellulosic fabric which comprises compressing the fabric, parchmentizing it and then exposing it to the action of sulphuric acid below parchmentizing strength.

- 14. The process of treating cellulo-sic fabric which comprises compressing the fabric, parchmentizing it with strong sulphuric acid and then exposing it to the action of sulphuric acid of less than parchmentizing strength.

15. The process of treating cotton fabric which comprises incompletely parchmentizing the fabric with sulphuric acid of somewhat less than 1.55 spec. grav. in presence of formaldehyde and then softening the fabric by exposure to sulphuric acid of less than parchmentlzing strength.

16. The process of treating cotton fabric which comprises treating the fabric with strong sulphuric acid of parchmentizing strength and then softening the fabric by exposure to sulphuric acid of less strength than the aforesaid strong acid.

17. Parchmentized cellulosic fabrics which have been softened by treatment with relatively dilute acid.

18. Compressed and parchmentized cotton fabrics which have been softened by treatment with relatively dilute acid.

19. The process of treating cotton fabric which comprises compressing and parchmentizing a fabric, and then softening said fabric by treatment with dilute acid.

In witness whereof, we have hereunto signed our names this 11th day of November, 1924, in the presence of two subscribing Witnesses.

ROBINSQN PERCY FOULDS. FRANK LESLIE BARRETT.

Witnesses:

J OHN W. THOMAS, WALLACE E. MOESSNER. 

